A Pilates chair exercise apparatus has a frame configured to rest on a horizontal surface, an inverted Y shaped seat support member fastened to an upper portion of the frame, a seat fastened to an upper end of the seat support, and a pair of parallel arms each having a proximal end fastened to the frame and a foot support fastened to a distal end of the arm, wherein each arm is biased away from the frame. A rotary torque unit mounted to the frame beneath the seat biases each of the arms. The rotary torque unit includes a rotary spring cassette that carries a plurality of flat coil springs each having only one end fastened to an axle at one end of one of the arms. Combinations of the springs in the spring cassette may be user selected without the user leaving the seat of the chair exercise apparatus.